Wireless communication has extensive applications in consumer and business markets. Among the many communication applications/systems are: fixed wireless, unlicensed (FCC) wireless, local area network (LAN), cordless telephony, personal base station, telemetry, mobile wireless, and other digital data processing applications. While each of these applications utilizes spread spectrum communications, they generally utilize unique and incompatible spreading protocols for signal transmissions. This corresponds to unique despreading protocols and algorithms for receiving the signals. Consequently, each application may require unique hardware, software, and methodologies for despreading. This practice can be costly in terms of design, testing, manufacturing, and infrastructure resources. As a result, a need arises to overcome the limitations associated with the varied hardware, software, and methodology of despreading digital signals for each of the varied wireless applications.
Complete demodulation of the radio waveform requires that the signal be processed by a specific step referred to as ‘despreading.’ The channel codes utilized for despreading relate to the complexity of the radio receiver design and channel width of the transmission. As new generations of protocols and hardware arise in any of the varied applications, they are sometimes sufficiently different from the previous generation as to render legacy systems incompatible or unusable. This situation arises from the equipment that has been developed using a standard-centric perspective. Consequently, new software, hardware, or infrastructure may be required to accommodate a new protocol in a given despreader application. Again, this practice can be costly in terms of design, testing, manufacturing, and infrastructure resources. Consequently, a need arises to overcome the lack of backward and forward compatibility associated with new generations of despreading protocols, hardware, and infrastructure within any of the varied wireless applications.
A despreader is a component used in spread-spectrum wireless communication receivers as a subsystem required to detect a signal. A despreader receives a spread spectrum data signal and performs inner-product operations with known despreading code sequences to despread the signal and form a symbol. One significant performance barrier in any communication system is the degradation of a data signal due to noise. A despreader accumulates signal energy as part of the overall despreader function. However, a noise or interference portion of a received signal can affect the resulting detection statistic, e.g., symbol, of the data signal generated by the despreader. Furthermore, variations in spreading factors are also used to accommodate multiple data rate transmission. Thus, a need arises to overcome limitations of noise and interference portions of the data signal. In addition, a need arises for a method to overcome the limitations associated with the variations and incompatibility of different spreading factors used to spread a signal at a transmitter device.
Unfortunately, the noise and interference portion of a data signal is frequently unstable. That is, the noise level in a signal can vary widely over time in a real-world environment. For example, weather, geographical interferences, electromagnetic interferences, distance between a base station and a mobile handset, speed of a mobile handset, transmissions from other users, etc. can contribute to the variation in the noise levels. If an accumulation length is selected for one noise condition, it may not be efficient for another noise condition. Thus, a need arises for a method to perform despreading functions that overcome the limitations of variation in the noise level of a signal under different operating environments.